The present invention relates to imaging devices and preferred embodiments relate, more particularly, to scintillation cameras used, e.g., in medical imaging and/or the like.
In various environments, such as, e.g., in medical environments, imaging devices can include detectors that detect electromagnetic radiation emitted from, e.g., radioactive isotopes or the like within a patient or the like. The detectors can involve, e.g., gamma scintillation cameras or the like that pick up, e.g., gamma rays emitted by the isotope. By way of example, while a patient lies motionless on a test table or the like, a gamma scintillation camera can be used to acquire images and record them on a computer for analysis.
Existing scintillation cameras experience spatial distortion that requires linearity correction (LC). A significant amount of effort has been made seeking to correct spatial or linearity distortion (along with, e.g., the companion energy and flood corrections). Existing methods can be divided into, e.g., two categories.
A first category is illustrated in U.S. Pat. No. 3,745,345 (the '345 patent) entitled Radiation Imaging Device, the entire disclosure of which is incorporated herein by reference. Here, a camera head is covered by a lead mask having a grid of pinhole apertures. A sheet source of radiation causes each aperture to illuminate a scintillation crystal. The camera then records an apparent location of an event in the crystal. There is a difference between the actual pinholes and the apparent events as located by the camera that is representative of spatial distortion at the respective locations on the camera face. Accordingly, a correction factor is needed for each point in a stored array.
A second category is illustrated in U.S. Pat. No. 4,212,061 entitled Radiation Signal Processing and U.S. Pat. No. 4,316,257 entitled Dynamic Modification Of Spatial Distortion Correction Capabilities Of Scintillation Camera, which involve spatial correction. For calibration, a lead mask having slit apertures is used. The camera is exposed to a radiation source, first with the mask in x lines and then with the mask in y lines. For each such exposure orientation, a series of transverse peak measurements at select intervals is developed. An analytical expression is generated to represent event coordinates between calibration intervals. Each orientation exposure, thus, produces one of a pair of calibration coordinates, which in turn permit direct correspondence to associated spatial coordinates. Among other deficiencies in this method, this method can take more than one hour of time by itself. It also requires additional preparation such as ‘centering and gain’. Moreover, this method requires use of multiple masks wastes time and money and increases equipment downtime.
Although there has been a significant amount of effort applied in the development of algorithms for LC, the lead masks used in the processes have received little attention. In fact, pinhole apertures utilized in existing devices have involved pinhole apertures arranged in a uniform and rectangular distribution (such as, e.g., depicted in FIG. 1 and depicted in FIG. 2 of the '345 patent). This existing design has a number of deficiencies, such as, e.g.: a) generating a low number of data points; and b) being less reliable where spatial distortion is more severe, such as, e.g., proximate edges and/or when thicker crystals are employed. In addition, existing lead masks do not enhance functionality in the overall calibration process, such as, e.g., to enable shorter calibration times and/or higher accuracies.
While a variety of methods and apparatuses are known, there remains a need for improved methods and apparatuses overcoming the above and/or other problems.